The primary goal of the proposed study is to conduct a longitudinal, multimodal assessment of Veteran sleep and suicide during the period following psychiatric hospitalization. Veterans and military personnel account for 18% of all known suicides in the United States, with 20 Veterans dying each day of suicide and 900 attempting suicide monthly. While multiple risk factors have been implicated in suicide behavior, insufficient sleep is consistently associated with elevated suicide risk. Since sleep difficulties often drive Veterans into treatment, sleep problems may be an optimal target for suicide prevention. Unfortunately the exact link between inadequate sleep and suicide risk is unclear and research is mixed regarding which specific types of sleep problems are associated with suicide and which mechanisms are driving the sleep-suicide link. The goal of this study is to examine the link between sleep and suicide ideation and related behaviors in a sample of high risk Veterans. One hundred and forty Veterans will be recruited during inpatient hospitalization and followed over 6 months following hospital discharge. Sleep and suicide will be assessed using a combination of actigraphy and Ecological Momentary Assessment (EMA). EMA will assess mechanisms hypothesized to drive the relationship between sleep and suicide including emotional reactivity and impulsivity. EMA devices will be able to capture daily changes in the hypothesized mechanisms, sleep parameters, and suicide thoughts and behaviors. The primary objective will be to examine how sleep impacts suicidal ideation and behavior and to determine which specific sleep parameters influence suicide thoughts and behaviors.